Activation of poly (ADP-ribose) polymerase 1 (PARP1) can lead to cell death during ischemia and other conditions that cause oxidative stress. PARP1 -mediated cell death is linked to NAD+ depletion and ATP depletion, but the biochemical events leading from PARP1 activation to cell death remain uncertain. The studies proposed here are based on recent findings in this laboratory showing that a) PARP1 activation leads to a profound depletion in cellular adenine nucleotide pool; b) NAD+ depletion caused by PARP1 activation leads to a block in glucose utilization; and c) PARP1 activation contributes to oxidative stress. Importantly, interventions that target reversal of these biochemical changes are effective if preventing PARP1 -mediated cell death at time points after PARP1 activation, an aspect with relevance to the treatment of ischemia-reperfusion and related disorders. An obstacle to this treatment approach in vivo, however, is that the blood-brain-barrier normally impedes access of adenine nucleotides and other compounds to the brain parenchyma. Here we propose to try several methods of crossing the BBB in a model of ischemia reperfusion. We also aim to further delineate the mechanisms by which PARP1 activation leads to cell death, in particular effects of PARP1 activation on oxidative stress and mitochondrial metabolism. PARP1 4- mice, SOD2 +/mice, and crosses of these strains will be used to elucidate the effects of secondary oxidative stress and endogenous protective mechanisms after PARP1 activation. Cell culture models will be used to fully characterize the downstream mechanisms of PARAGUAY -mediated cell death, and a mouse stroke model will be used to corroborate the in vitro findings and to test several approaches for delivering adenine nucleotide precursors and mitochondrial substrates across the blood-barrier in the post-ischemic period.